The Impella (Abiomed, Inc., Danvers, MA USA) is a platform technology designed for the support of patients with cardiogenic shock. Support of the failing left ventricle (LV) is achieved with miniaturized pumps inserted into the LV across the aortic valve. They come in three different versions: the Impella 2.5 that is inserted percutaneously, the Impella LD that is inserted directly into the ascending aorta after sternotomy, and the Impella 5.0 (LP5.0) that is inserted peripherally through a femoral artery cutdown. There is also a version designed for right ventricular support. The Impella technology is based on a microaxial pump that can safely pump blood in the larger versions at rates of up to 5.0 L per minute, thereby providing almost complete circulatory support for the severely ill patient. The pump is intended for short-term use of up to 10 days. The intention is to support patients to recovery or as a bridge to more permanent solutions such as a LV assist device. Early experience with the direct version in Europe showed a reduction in mortality of patients with postcardiotomy failure1 and diverse applications in severely compromised patients.2,3 Detailed product monographs are available through the company Web site at www.abiomed.com.
Our institution has the first and largest North American experience with insertion of the pump. To date we have inserted 41 of the Impella devices (33 LP5.0 and 8 right ventricular support devices). In the process of implementing this new technology, we independently developed novel techniques for insertion of the device. These techniques differ significantly from the U-stitch approach described by the manufacturer.
Both fluoroscopy and transesophageal echocardiogram (TEE) are essential, and each imaging modality provides unique information. The Impella 5.0 is designed for insertion through a femoral cutdown. The motor housing of the device is 21 Fr and requires a larger peripheral artery even though the driveline is only 9 Fr. As the patient population is very ill, prepping and draping the chest may be prudent. The incision for the femoral cutdown should always be fashioned to expose the largest portion of the common femoral artery. For all insertion techniques, systemic heparinization is titrated to achieve an activated clotting time of >250 seconds during the procedure.
If the device is being inserted into a patient on cardiopulmonary bypass, passage of the pigtail into the LV can be aided by decreasing cardiopulmonary bypass support. This will allow LV ejection and, thus, opening of the aortic valve.
The first technique uses a beveled graft anastomosed to the largest portion of the common femoral artery. The artery is exposed, heparin given, and the artery clamped proximally and distally. An incision is made longitudinally in the artery, and an 8-mm Hemashield graft (Boston Scientific, Natick, MA) is sewn to the opening using a 5-0 prolene suture. The graft must attach to the artery at a 45-degree angle to facilitate sheath and device introduction. Once it is de-aired and the clamps are removed, the graft then serves as a workstation. At this stage, the graft can be controlled temporarily with a Fogarty clamp or manually. Next, a 7-Fr femoral sheath is introduced into the graft upward toward the iliac artery. A gentle curve on the sheath will facilitate passing the anastomosis, and a heavy 0-0 silk tied around the sheath will control bleeding at this stage (Fig. 1).
With the sheath in place, a 150-cm 0.035-in flexible tip Glidewire (Terumo Medical, Corp., Somerset, NJ) is inserted through the sheath and passed across the aortic valve into the LV using fluoroscopy. Insertion of the guidewire is facilitated with a 6-Fr pigtail catheter as the pigtail often slides across the aortic valve easily. With the pigtail in place, the guidewire is removed and the prepackaged Impella guidewire then inserted into the LV. In all our cases, we have left a large amount of redundant wire in the LV to ensure that the wire does not slip out. The pigtail and femoral sheath are removed, and the graft is clamped on the wire.
The Impella pump is prepared in the usual fashion and then inserted on the guidewire being careful that the guidewire leaves the outlet housing in the marked position. Gently hyperextending the angled portion of the cannula past the straight position facilitates the guidewire leaving the housing correctly. The Impella 5.0 is passed through the graft with care being taken to minimize any trauma to the device. The wire then acts as a rail and the device is easily inserted into the LV. Appropriate positioning is determined with a combination of fluoroscopy, TEE, and establishment of pulsatility on the pressure sensor of the device. During this procedure, the pump or driveline should never be clamped.
With the pump in place, the graft should then be shortened to 3 or 4 cm and the repositioning unit inserted into the graft. (The repositioning unit is a sheath that comes attached in a preassembled fashion to the Impella driveline and allows for the device to be moved in or out without manipulating the artery.) The graft is tied around the yellow bevel of the repositioning unit (Fig. 2). It is important that the graft be buried within the wound substantially to avoid contamination.
The graft can facilitate removal of the device at the bedside as only the graft need be controlled. We have tied a heavy silk ligature around the base of the graft near the anastomosis and then cut off the remaining portion of the graft.
The graft technique is particularly helpful in a patient with a small femoral artery and ensures that there will be good distal flow, thereby minimizing limb ischemia. We believe that it is also helpful for a surgeon inexperienced with device implant by making control of the artery and pump insertion easier. We have used the graft technique in 11 cases with the indication being either a small femoral artery (less than 10 mm in size) or surgeon preference. Use of an axillary artery graft has also been described.4
In the remaining 22 cases, we used a purse-string technique. A 3-cm skin incision is made over the femoral artery and the vessel exposed. Proximal and distal controls are obtained. A 4-0 prolene is used to create a purse-string suture on the largest portion of the femoral artery, and a short tourniquet is applied and used to control hemostasis during device insertion. The purse string needs to be large enough to allow passage of the Impella device (Fig. 3). The femoral artery is punctured directly with an Angiocath needle through the area circumscribed by the purse string. A glidewire is then inserted and the Angiocath removed and replaced with a 6-Fr All-Purpose Pigtail catheter, which is then advanced under fluoroscopy until it crosses the aortic valve into the LV.
Once the pigtail catheter is within the LV, the guidewire is exchanged for the Impella guidewire and the pigtail removed. A separate stab incision is made in the skin distal to the femoral incision and the Impella guidewire brought out through the stab. The Impella 5.0 device is passed through the separate stab incision and then through the previously fashioned purse string in the femoral artery, allowing the passage of the device. The pump portion of the LP5.0 should be covered with the finger from a sterile glove to prevent clogging of the inlet and outlet with fat and debris. The glove tip is removed before inserting the device into the femoral artery. The previous puncture through the purse string in the femoral artery will need to be enlarged with a longitudinal arteriotomy (Fig. 4). Under fluoroscopy, the device can be seen easily and advancement into the LV followed. The incision is then closed in the usual fashion with the short tourniquet buried beneath.
The purse-string technique is simple, and the device can be inserted rapidly. The separate stab incision may be beneficial in preventing infection as the device and drive line enter remote to the incision through a small wound that will easily epithelialize. Device removal can be done in the critical care unit under local anesthetic and hemostasis achieved by simply securing the purse string. In our series, most of devices were removed at the bedside and not in the operating room. With either the graft or purse-string technique, the blood loss has always been minimal because of the ease of controlling the femoral artery.
In both techniques, final placement is confirmed with TEE where the inlet and outlet are equidistant from the aortic valve (Fig. 5). A TEE long-axis view of the aortic valve is used. The ventricular tip of the device should not restrict the anterior leaflet of the mitral valve and should measure 3 to 4 cm from the aortic valve. Once the guidewire is removed, the Impella can then be started at level P2 and increased in a stepwise fashion until level P8 or 9 have been achieved. When the device is activated, color Doppler is used to confirm flow from the outlet cannula above the aortic valve.
The driveline should be well secured onto the patients' thigh. Position of the device is usually quite stable, and extubation of the patient is possible in selected cases.
We have not experienced infectious complications specific to the LP5.0 device. However, it is common, for the patients to have significant coagulopathy at the time of insertion of the device (usually because of liver failure and antiplatelet medication), and there is frequently blood loss from the femoral artery cutdown. The blood loss is significantly minimized with careful surgical technique and can be controlled with local pressure. It usually improves dramatically with the restitution of adequate tissue perfusion and the consequent improvement in hepatic function. With the above techniques, we have not had bleeding that has required reoperation.
In our experience, the Impella 5.0 represents a revolutionary technology for the short-term support of the acutely ill patient with LV failure. It dramatically stabilizes most patients' renal and hepatic function and provides the opportunity to assess the patients' suitability for transplant, assess neurologic status, or allow the necessary time for recovery.
The authors thank Abiomed for supplying the color micrographs.
1. Siegenthaler MP, Brehm K, Strecker T, et al. Impella Recover microaxial left ventricular assist device reduces mortality for postcardiotomy failure: a three-center experience. J Thorac Cardiovasc Surg.
2. Garatti A, Colombo T, Russo C, et al. Left ventricular mechanical support with the Impella Recover left direct microaxial blood pump: a single-centre experience. Artif Organs.
3. Jurmann MJ, Siniawski H, Erb M, et al. Initial experience with miniature axial flow ventricular assist devices for postcardiotomy heart failure. Ann Thorac Surg.
4. Sassard T, Scalabre A, Bonnefoy E, et al. The right axillary artery approach for the Impella Recover LP 5.0 microaxial pump. Ann Thorac Surg.
The Impella system (Abiomed, Inc., Danvers, MA) is a short-term left ventricular assist device that is typically inserted through the common femoral artery. The authors describe two novel insertion techniques for this device, which are different from those described by the manufacturer. These were developed by the group at the University of British Columbia that has had a large experience with this device. They were able to remove most of the devices at bedside and not in the operating room using these techniques. This technology is being increasingly used for the short-term support of critically ill patients with cardiogenic shock. It is less invasive than comparable devices and provides support at rates of up to 5 L/min. For surgeons just beginning their experiences with this new technology, this article will provide useful and practical information regarding their insertion and removal.